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difference takes place in the quantity of the gas,according to the degree of heat and other cir-cumftances.

Another method of obtaining carburetted hy-drogen is to put coal, wood, peat, &c. into anyconvenient veflel, an earthen or iron retort forexample, and heat it flowly to rednefs.

Molt animal inflammable fubftances, fuch asfilk, fat, wax, and the like, yield this gas asfreely as vegetable matters by a fimilar treat-ment. This was difcovered by Berthollet , inhis moll mafterly refearches on the nature ofanimal matter and of ammonia; and as the gasin' this cafe is not mixed with an unufual portionof azot, he fagacioufly conjectured and after-wards fully proved that the azot, certainly con-tained in animal matters, went to conftitute theammonia which is always given off in the pro-cefs.

Carburetted hydrogen (or at leaft a gas whichgives carbonic acid and water by combuftionwith oxygen) is alfo generated in abundancewhen charcoal not previoufly dried is diftilledper fe in clofe veflels, and continues to be givenoff till it has been heated fully red-hot for aboutan hour, after which it ceafes, and the charcoal,as mentioned under the two preceding articles,is now pure. A fimilar, though fomewhat dif-ferent procefs for obtaining the gas, is to enclofepowdered charcoal in a tube palling through afurnace, to confine the charcoal loofely by apellet of clay at each end of the tube, to heat itred hot, and in that fituation to fend through itthe vapour of water kept boiling in a fmall retortattached to one end of the tube. Much carbonicacid gas is generated in this way, and when thisis removed the remaining gas is inflammable.

Laftly, this gas may be obtained by the directunion of its conftituent parts. If hydrogen gasis palled feven or eight times fucceffively throughan iron tube containing charcoal and heated redhot, a diminution of the bulk of the gas takesplace, the hydrogen diffolves a portion of thecharcoal, and then afliimes the properties ofcarburetted hydrogen. b

A molt curious variety of hydrocarbonat gaswas difcovered by the afl'oeiated Dutch chemifts(Van Dieman, Trooltwyck, and others), whichis procured from ether or alcohol, and has theremarkable property of generating or depofitinga heavy oil when in contact with the oxymuri-atic gas. Hence it has been termed oily car-htiretted hydrogen , or olefiant gas. It appears toconfift of carburetted hydrogen, fuperfaturatedwith a large portion of carbonous matter in fome* Deformes & Clement. An. Ch. tom. 39- * Phil- Jour,

unknown ftate of combination, and hence itrequires a much greater proportion of oxygenfor faturation, and alfo produces a much largerquantity of carbonic acid than the other hydrocar-bonats : it is alfo much heavier. The mode andpreparation of this Angular gas, and its peculiarproperties, will be feparately deferibed, but itmay be added that according to Mr. W. Henry’sexperiments, c the olefiant gas appears to bealfo contained partially in the hydro'carbonatfrom coal, from wax, and fome other fubftances,and greatly to contribute to the quantity of lightand heat, which thefe gaffes give out, as well asto the proportion of carbonic acid.

Hydrocarbonat gas is Angularly affefted bythe eledtric fpark. Dr. Auftin d found that ontaking the eleftric fpark fucceffively throughthis gas obtained from the acetite of potafltand in confiderable purity, the bulk of the gasenlarged after every fhock; and by continuing itfrom 200 to 300 times it expanded to nearlytwice its original dimenfions. Examined afterthis expanfion it was found however to be asinflammable as before, and by the teft of lime-water no carbonic acid was generated. Dr. A.concludes that the enlargement can be onlyowing to the production of a quantity of hydro-gen, and makes fome inferences from the ex-periments, the moft important of which areihewn to he improbable by the fubfequent ex-periments of Mr. Henry on the fame fubjecl.Mr. H. fully fhews e that there is no dtf ructionof carbon by this procefs, fince the fame quan-tity of carbonic acid is produced by oxygen afterelectrization of the carburetted hydrogen as be-fore it. He likewife makes it appear probablethat the water held in folution by the gas is thechief agent in this expanfion, fince when thegas is carefully dried by cauftic alkali, no con-tinuance of the electrization will enlarge it be-yond one-fixth of its bulk, but when the contact -of water is admitted, it expands to double itsbulk as before. Perhaps the difeovery of thecarbonous oxyd will explain this fact. It is notimprobable that the carbon of the gas may unltewith the oxygen of the water and produce thegafeous carbonous oxyd, which would not giveany precipitate with lime-water, and the bulkof the gas would be enlarged both by the car-bonous oxyd and by the hydrogen of the water,and alfo by the expanfion which the hydrogenof the hydrocarbonat would undergo after thecarbon was feparated from it: whilft the actualquantity of carbon remaining the fame, as muchcarbonic acid would be generated by compleat

8vo. vol.ii, * Phil. Tranf. vol. 80. ' Ibid, veffi 87.

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